js字符串转字节

function stringToByte (str) {
  var len, c;
  len = str.length;
  var bytes = [];
  for (var i = 0; i < len; i++) {
    c = str.charCodeAt(i);
    if (c >= 0x010000 && c <= 0x10FFFF) {
      bytes.push(((c >> 18) & 0x07) | 0xF0);
      bytes.push(((c >> 12) & 0x3F) | 0x80);
      bytes.push(((c >> 6) & 0x3F) | 0x80);
      bytes.push((c & 0x3F) | 0x80);
    } else if (c >= 0x000800 && c <= 0x00FFFF) {
      bytes.push(((c >> 12) & 0x0F) | 0xE0);
      bytes.push(((c >> 6) & 0x3F) | 0x80);
      bytes.push((c & 0x3F) | 0x80);
    } else if (c >= 0x000080 && c <= 0x0007FF) {
      bytes.push(((c >> 6) & 0x1F) | 0xC0);
      bytes.push((c & 0x3F) | 0x80);
    } else {
      bytes.push(c & 0xFF);
    }
  }
  return bytes;
}

const r = stringToByte("数据数量限制2000，导出失败！")
console.log(r);
console.log(r.length);

[
 230, 149, 176, 230, 141, 174, 230, 149,
 176, 233, 135, 143, 233, 153, 144, 229,
 136, 182, 50, 48, 48, 48, 239, 188,
 140, 229, 175, 188, 229, 135, 186, 229,
 164, 177, 232, 180, 165, 239, 188, 129
 ]
 40